Breech bolt for automatic firearms



Nov. 8, 1932. R. VON FROMMER 1,886,609

BREECH BOLT FOR AUTOMATIC FIREARMS Filed Oct. 25. 1930 W VM 3% Patented Nov. 8,1932

RUDOLF VON FROMMER, OF BUDAPEST, HUNGARY BREEGH BOLT FOR AUTOMATIC FIREARMS Application filed October 25, 1930, Serial No.

This invention relates to automatic fire arms comprising a hammer adapted to strike the rear end of a firing pin arranged to be normally kept away from the cartridge primer by a retaining spring and located in a straight-pull breech bolt comprising a sleeve portion and a block portion adapted to be rotated and displaced axially with respect to the sleeve portion so as to increase the effective length of the breech bolt and withdraw into the breech bolt the rear end of the firing pin thus preventing discharge of the fire arm accidentally with the breech bolt open.

The retaining spring referred to above is provided in order to avoid unintentional firing when closing the breech bolt, but experience has shown that the requirements cannot be met with this arrangement as upon a very fast shifting of the breech bolt in the forward direction by the closing spring and very fast shifting of the sleeve portion of the breech bolt with respect to the block portion, the firing pin gets such a great acceleration that the retaining spring may be unable to fulfil its task, that is to say the firing pin may touch the primer and also fire the cartridge. This drawback is caused by the fact that the strength of the retaining spring is very limited, as this spring must be much weaker than the firing spring.

In order to avoid this drawback the firing pin is, according to the present invention, guided in the sleeve portion of the breech bolt so as not to be rotatable therein, the

block portion of the breech bolt being rotatable around the firing pin, and the firing pin is provided with a projection and the block portion with a retaining surface interrupted by a cavity, or conversely, the firing pin has the retaining surface with the cavity and the block portion the projection, in such a manner that the projection is only opposite the cavity in the fully closed position of the breech bolt, whilst in all other 491,131, and in Hungary November '9, 1929. 1

positions the projection is opposite the retaining surface. 1 In the accompanying drawing one form of the invention is shown by way of example.

Fig. l is a sectional View of the closed ,1. breech bolt.

-Fig. 2 is the same view in the open position of the breech bolt.

Fig. 3 is a rear elevation of the closed block portion of the breech bolt.

Fig. 4 is the same elevation in the open position of the block portion.

Fig. 5 is a sectional view taken on the line AB of Fig. 1.

In the sleeve portion 1 of the breech bolt is arranged the block portion 3 of the breech bolt jointed with the sleeve portion by spiral grooves and tongues 2 so as to allow the shifting and. rotating of the block portion in known manner. The firing pin 5 arranged in the sleeve portion and. in the block portion 3 of the breech bolt co-operates with the helical spring 6 which presses the pin constantly backwards. The backward movement of the pin is limited by a stop 7. On the pin 5 which is in one piece with the firing point is provided a collar 8 and a projection 9, as well as a guiding portion 10 (see also Fig. 5) which prevents turning of the pin around its longitudinal axis. In order to enable the block portion 3 to rotate with respect to the firing pin, a groove 14 is provided in it. This block portlon is also provided with a cavity 11, which interrupts the retaining surface 13 provided at the end of the block portion. When the breech bolt is in its fully closed position (Figs. 1 and 3) the cavity 11 is situated opposite the projection 9 of the firing pin 5 thus enabling the latter to move forward under the action of the hammer 12 whereby the projection enters the cavity. There is no other position in which this movement of the firing pin can take place, as in all other positions the cavity 11- is swung away from the projection 9 (see Fig. 4) the latter being held in position by the portion 10. The projection 9 is then opposite the retaining surface 13 of the block portion and prevents the pin from finishing its forward movement.

As aforesaid, it is obviously possible to arrange the retaining surface and the cavity on the firing pin, and accordingly the projection co-operating With them on the breech block.

I claim:

In an; automatic fire armofthe kind having a straight-pullbreech comprising a sleeve portion, and a block portion adapted to be 15 rotated and displaced axially with; respect to the sleeve portion, a firing p'i-n around which the said block portion is rotatable, a spring adapted to press backwards said fir ing pin, means preventing said firingpin 20 from rotation in the said sleeve portion, a hammer'adapted to strike the rearend of the said firing pin, a projection and, a retaining-surface one of them being provided on the firing pin andthe other on the block portion, the, retaining surface having a cavity interrupting said retaining surface, said projection being adapted to penetrate into said cavity, the latterbeing arranged to be aligned With said projection only in the fully bolted position of the breech.-

In testimony whereof I aflix my signature.

RUDOLF; VON.'FROMMER. 

